Area and Perimeter
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ISEE Middle Level: Mathematics Achievement › Area and Perimeter
A rectangular garden measures 10 meters by 15 meters. A walkway of uniform width of 2 meters is built around the outside of the garden. What is the area of the walkway?
150 square meters
100 square meters
266 square meters
116 square meters
Explanation
The area of the garden is \(10 \times 15 = 150\) square meters. The walkway adds 2 meters to each side of the garden. So, the new length is \(15 + 2 + 2 = 19\) meters, and the new width is \(10 + 2 + 2 = 14\) meters. The total area of the garden with the walkway is \(19 \times 14 = 266\) square meters. To find the area of the walkway, subtract the garden's area from the total area: \(266 - 150 = 116\) square meters.
A rectangular park has a perimeter of 120 meters. Its length is 10 meters longer than its width. What is the area of the park?
900 square meters
1000 square meters
875 square meters
950 square meters
Explanation
Let the width of the park be \(w\) meters. The length is \(w+10\) meters. The perimeter is given by \(P=2(L+W)\), so \(120 = 2((w+10)+w)\). Simplifying gives \(120 = 2(2w+10)\), which becomes \(60 = 2w+10\). Subtracting 10 gives \(50 = 2w\), so the width \(w=25\) meters. The length is \(25+10=35\) meters. The area of the park is \(L \times W = 35 \times 25 = 875\) square meters.
A square-shaped garden has an area of 225 square feet. If a farmer wants to build a fence around the garden, how many feet of fencing will be required?
225 feet
15 feet
60 feet
30 feet
Explanation
The amount of fencing required is the perimeter of the garden. The area of the square is given as 225 square feet. The formula for the area of a square is \(A = s^2\), where \(s\) is the side length. So, \(s^2 = 225\). To find the side length, take the square root of the area: \(s = \sqrt{225} = 15\) feet. The perimeter of a square is \(P = 4s\). So, the required fencing is \(4 \times 15 = 60\) feet.
The area of a square is 64 square centimeters. A rectangle has the same perimeter as the square. If the length of the rectangle is 10 centimeters, what is the area of the rectangle in square centimeters?
100 square centimeters
80 square centimeters
64 square centimeters
60 square centimeters
Explanation
First, find the side length of the square. If the area is 64 cm², the side length is \(\sqrt{64} = 8\) cm. The perimeter of the square is \(4 \times 8 = 32\) cm. The rectangle has the same perimeter, 32 cm. The formula for the perimeter of a rectangle is \(P = 2(L+W)\). We have \(32 = 2(10+W)\). Dividing by 2 gives \(16 = 10+W\), so the width \(W = 6\) cm. The area of the rectangle is \(L \times W = 10 \times 6 = 60\) square centimeters.
The length of a rectangle is twice its width. If the area of the rectangle is 98 square feet, what is its perimeter in feet?
42 feet
49 feet
35 feet
21 feet
Explanation
Let the width be \(w\). The length is \(2w\). The area is \(L \times W\), so \((2w)(w) = 98\). This gives \(2w^2 = 98\). Dividing by 2, we get \(w^2 = 49\), so the width \(w = 7\) feet. The length is \(2 \times 7 = 14\) feet. The perimeter is \(2(L+W) = 2(14+7) = 2(21) = 42\) feet.
The perimeter of Square X is 4 times the perimeter of Square Y. The area of Square X is how many times the area of Square Y?
64 times
16 times
4 times
8 times
Explanation
Let the side length of Square Y be \(s_y\). Its perimeter is \(4s_y\). Let the side length of Square X be \(s_x\). Its perimeter is \(4s_x\). We are given \(4s_x = 4(4s_y)\), which simplifies to \(4s_x = 16s_y\), and further to \(s_x = 4s_y\). The area of Square Y is \(A_y = (s_y)^2\). The area of Square X is \(A_x = (s_x)^2 = (4s_y)^2 = 16(s_y)^2\). Therefore, the area of Square X is 16 times the area of Square Y.
If the length and width of a rectangle are both tripled, which statement accurately describes the change in its perimeter and area?
The perimeter is tripled, and the area is nine times as large.
The perimeter is tripled, and the area is tripled.
The perimeter is six times as large, and the area is tripled.
The perimeter is nine times as large, and the area is nine times as large.
Explanation
Let the original length and width be L and W. The original perimeter is \(P = 2(L+W)\) and the original area is \(A = LW\). The new length and width are 3L and 3W. The new perimeter is \(P_{new} = 2(3L+3W) = 2(3(L+W)) = 3(2(L+W)) = 3P\). The new area is \(A_{new} = (3L)(3W) = 9(LW) = 9A\). So, the perimeter is tripled and the area becomes nine times as large.
A piece of wire 60 inches long is bent to form a square. The same wire is then re-bent to form a rectangle with a length of 18 inches. What is the positive difference in area between the square and the rectangle?
9 square inches
99 square inches
225 square inches
15 square inches
Explanation
The length of the wire is the perimeter of both shapes. For the square, the perimeter is 60 inches, so each side is \(60 \div 4 = 15\) inches. The area of the square is \(15 \times 15 = 225\) square inches. For the rectangle, the perimeter is also 60 inches. Using \(P=2(L+W)\), we have \(60 = 2(18+W)\). This simplifies to \(30 = 18+W\), so the width is \(12\) inches. The area of the rectangle is \(18 \times 12 = 216\) square inches. The difference in areas is \(225 - 216 = 9\) square inches.
A rectangular piece of cardboard measures 15 inches by 20 inches. A square with a side length of 4 inches is cut from each of the four corners. What is the perimeter of the remaining piece of cardboard?
38 inches
70 inches
54 inches
62 inches
Explanation
The perimeter of the original rectangle is \(2(15+20) = 2(35) = 70\) inches. When a square is cut from a corner, two segments of the original perimeter are removed, but two new segments of the same length are added. For example, at one corner, a 4-inch segment from the length and a 4-inch segment from the width are conceptually removed. They are replaced by the two inner sides of the cut-out square, each 4 inches long. The net change to the perimeter at each corner is \(-4 - 4 + 4 + 4 = 0\). Since this happens at all four corners, the perimeter of the new shape is the same as the original perimeter, which is 70 inches.
The length of a rectangular sign is \((3x + 2)\) meters and its width is \(x\) meters. If the perimeter of the sign is 52 meters, what is its area in square meters?
20 square meters
120 square meters
6 square meters
52 square meters
Explanation
The formula for the perimeter of a rectangle is \(P = 2(L+W)\). Substitute the expressions for length and width: \(52 = 2((3x+2) + x)\). Simplify the expression inside the parentheses: \(52 = 2(4x+2)\). Distribute the 2: \(52 = 8x + 4\). Subtract 4 from both sides: \(48 = 8x\). Divide by 8 to find \(x=6\). Now find the dimensions: the width is \(x = 6\) meters, and the length is \(3(6) + 2 = 18 + 2 = 20\) meters. The area is length times width: \(A = 20 \times 6 = 120\) square meters.